Field of the Invention
The present invention relates to a wafer processing method for removing an annular reinforcing portion from a wafer having a device area, the annular reinforcing portion being formed around the device area.
Description of the Related Art
A wafer having a plurality of devices such as integrated circuits (ICs) and large scale integrations (LSIs) on the front side is divided into a plurality of individual chips corresponding to the plural devices by using a dicing apparatus or the like. These chips are widely used so as to be built in various electronic equipment. For the purposes of reducing the size and weight of electronic equipment, the thickness of the wafer is reduced to 50 to 100 μm, for example. However, such a thin wafer has low rigidity, and warpage may also occur. Accordingly, the wafer is difficult to handle. To cope with this problem, there has been proposed a method of grinding the back side of the wafer in a central area corresponding to a device area where the devices are formed, thereby forming an annular reinforcing portion along the outer circumference of the wafer to increase the rigidity of the wafer (see Japanese Patent Laid-open No. 2007-019461, for example).
There has also been proposed a method of removing the annular reinforcing portion from the wafer before dividing the wafer along division lines (see Japanese Patent Laid-open No. 2015-147231, for example). In the method described in Japanese Patent Laid-open No. 2015-147231, an adhesive tape is attached to the front side of the wafer, and the adhesive tape is supported at its peripheral portion to an annular frame, thereby supporting the wafer through the adhesive tape to the annular frame. In this condition, a boundary portion between the device area and the annular reinforcing portion (peripheral marginal area) is cut together with the adhesive tape by laser processing to thereby separate the annular reinforcing portion from the device area. Thereafter, the annular reinforcing portion is removed together with the annular frame from the wafer.